The present invention relates to a magnetic multilayer film having a high magnetoresistive effect, and more specifically to a multilayer film which shows the magnetoresistive effect in reading magnetic heads for use in magnetic disk apparatus.
As magnetic records have became highly dense, a material showing a high magnetoresistive effect is demanded for use in reading magnetic heads. The relative resistivity change of permalloy in current use is about 3%, and it is thus required that a new material should have a greater relative resistivity change exceeding this value.
As is shown in "Large Magnetoresistance of Field-Induced Giant Ferromagnetic Multilayers" which has been recently reported by Shinjo, et al., Journal of The Physical Society of Japan, Vol. 59, No.9, page 3061-3064, a relative resistivity change of 9.9% is observed in a magnetic film having a multilayer structure (Co/Cu/Ni--Fe/Co multilayer film).
As is shown in "Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices" described by Baibich, et al., Physical Review Letters, Vol. 61, No.21, page 2472-2475, the relative resistivity change is observed to be about 50% at 4.2K in a magnetic film having a multilayer structure (Fe/Cr multilayer film).
In the magnetic film having a multilayer structure described by Shinjyo, et al., however, the magnetic field strength required for the change in electric resistance is as large as about 50 Oe, so such a film has a problem in the sensitivity of magnetic fields when it is used as a sensor for detecting a weak magnetic field of magnetic heads.
In order to use a magnetic film having the aforementioned multilayer structure in magnetoresistive elements and magnetic heads, it is required that the resistance change should be large within the range in which outer magnetic fields are variable. Such a film has a problem in that a highly sensitive magnetoresistive element cannot be obtained, based only on the film structure described in the reference by Baibichi, et al.
Japanese Patent Laid-open Nos. 23681/1990 and 61572/1990 disclose other magnetoresistive elements in multilayer structure.